Vapor-entrainment pumps



May 26, 1954 H. JANCKE ETAL 3,134,534

VAPOR-ENTRAINMENT PUMPS Filed Feb. 16, 1961 3 Sheets-Sheet l lNv NToRsATTO RNEY 3 Sheets-Sheet 2 Filed Feb. 16, 1961 Cocu/awr INVENToRs AfA/vsJIq/vck-E BY A64/vs .Bee-rz ATTO R N EY May 26, 1964 H. JANCKE ETAL3,134,534

VAPOR-ENTRAINMENT PUMPS Filed Feb. 16, 1961 Tlc.

3 Sheets-Sheet 3 IN ENTORS Aly/ss ,4A/cme ATTORNEY United States PatentOiice 3,134,534 Patented May 26, 1964 Akademie der Wissenschaten zuBerlin, Berlin-Adlershot, Germany Filed Feb. 16, 1951, Ser. N 89,782Claims priority, application Germany Feb. 23, 1969 13 Claims. (Cl.230-101) The present invention relates to singleand multi-stagevapor-entrainment or condensation pumps and more particularly to a novelarrangement of a heating system providing very short heating and coolingperiods in such purnps.

It is known that in condensation-type pumps the entraining uid is heatedto evaporation and then conveyed in a gaseous state, from the boiler tothe ejector nozzle with a view to achieving the pressure required forthe operation of the pump. Upon leaving the nozzle, the vaporized uidcondenses on the enclosure walls, which are usually cooled by extraneousmeans, after which the huid returns in a liquid state to the reservoiror boiler.

In this type of arrangement it cannot be avoided that almost the entireamount of fluid has to be maintained at a relatively high evaporatingtemperature in the boiler although only a small portion thereof is beingevaporated for useV at any given moment. Consequently, it takes a longtime to heat up and to cool down the pump, resulting in diiculties whichare particularly evident in case of intermittent use. Various diusionpumps have been designed which incorporate special fast-cooling devicesin an attempt to overcome these dili'iculties.

The heat losses in these vapor-entrainment pumps originate not only fromthe necessity of removing the heat stored in the uid but also fromexcess evaporation of the entire tiuid surface. This circumstance alsoresults in undesirable heat losses of the vapor which becomesunnecessarily cooled on its way to the ejector nozzle.

It is an object of the present invention to provide a novelvapor-entrainment pump overcoming the dilculties and drawbacksexperienced with previous arrangements. In particular, object is toprovide in such systems a special delivery pump for conveying theentraining iluid to a region of the vapor-entrainment pump close to thenpzzle where the localized heating and evaporation takes piace.

It is another object to provide a vapor-entrainment pump wherein theriser tube leading to said region of localized heating is cooled so asto return as much entraining fluid as possible to theboiler.

The present invention represents a simple yet elective solution of thedrawbacks characteristic of hitherto known types of condensation orvapor-entrainment pumps. One of the main features of the inventionresides in the provision and disposition of the heating means adjacentthe nozzle or nozzles-of the pump, adjacent the zone of use, rather thanaround or within the uid reservoir or boiler, remote from the zone ofuse. A conventional type of delivery pump may be used for raising theiiuid from the reservoir to the region of the heating means.

It is a further object of the invention to provide a cooling jacketaround the riser tube of the delivery pump and/ or an overow tube whichreturns the excess fluid from the ejector means to the reservoir.

In a preferred embodiment using a conductive liquid metal, e.g. mercury,an electromagnetic pump is provided for conveying the entraining uid toa small pool adjacent the combined heating and ejector unit.Advantageously, the fluid in such a small pool can be heated by passingan electric current through the conductive liquid.

The invention oiiers several advantages over previous systems. The mostmarked dilierence is that the entire volume of fluid contained in thereservoir cools down to the coolant temperature shortly after thevapor-entrainment pump is disconnected. There is no need forcompensating temperature dierences between the heater at the bottom ofthe boiler and thecooling jacket.

lt is a further advantage of the arrangement of the present inventionthat the operating pressure at the ejector nozzle, or at each of severalnozzles of multi-stage systems, is simple to regulate. Thevapor-pressure regulation has a negligibly small time constant due tothe low heat capacity of the heated parts. Moreover, the heating of eachseparate nozzle stage in the multi-stage embodiment, can be controlledindividually. Y

In multi-stage vapor-entrainment pumps equipped with one or more stages,according to the present invention, the quantities of entraining duidsupplied to the individual stages can be easily adapted to the actualconsumption.

These and other features and advantages or" the invention will becomemore apparent in the following description and the enclosed drawings, inwhich:

FlG. l is a partly schematic sectional view of a preferred embodiment ofa single-stage vapor-entrainment pump according to the invention;

FlG. 2 is a similar View of a vapor-entrainment pump using anelectrically conductive liquid metal as the entraining fluid; and

FIG. 3 shows a schematic arrangement of a multi-stage vapor-entrainrnentpump having a high-pressure forevacuum stage connected in series withtwo diffusion-type stages.

In FIG. 1, the vapor-entrairnnent pump is shown to comprise a housing orshell 10 enclosing an inner shell lila having a lower portion whichforms a reservoir 11 containing the entraining fluid 12, which may bean-oil having low vapor pressure, as generally used in diffusion pumps.The Space between the shell and the housing serves as a cooling jacket13 provided with an inlet 13a and an outlet 13b through which a coolantis circulated. A conduit 14 serves to connect the entrainment pump to asuitable source to establish a fore vacuum (not shown), while a conduit15 provides a high-vacuum connection through which the pump may beconnected to the system to be evacuated.

Above the reservoir 11, a delivery pump 16 is arranged within the innershell 16a, with its inlet tube 16a reaching into the uid 12 in thereservoir 11 and with its outlet tube 16b rising substantially centrallywithin the shell 10a to the region of the ejector 17. The unit 17 ispreferably supported by flanges 17a and 17b attached to the coverportion of housing 1t). The ejector unit 17 has a recessed portion 17Cholding a pool 18 of the entrainment lluid supplied by the outlet orriser tube 1611 of delivery pump 16. A heater 19, shown here as a doubleannular electric heating element, fed from a source of current 21through a variable resistor 22 or other conventional means, is disposedto heat the liquid in the pool 1S. The ejector 17 also has one or morenozzles, two of which are shown at 2tlg and 2Gb. The delivery pump 16 isenergized from an electric source 23; this may be separate from oridentical with the source of current 21 for the heater.

The ejector unit 17 may be provided with an overow tube 24 the upper endof which is flush with the Huid level in pool 1S. Both the overliow tube24 and the riser tube 1617 of delivery pump 16 can be provided withcooling jackets 25a, 25h, respectively. These cooling systems may, ofcourse, be operated parallel with or independently from the coolingsystem of jacket. 13 of the housing 1i).

' mally held at relatively low temperature.

the gas Within the inner shell 16a is rareiiedrto a desired extent,`the'delivery pump 1J and vshortly 'thereafter the heater 19 are putinto operation. The duid 12 in reserlvoir 11 will remain substantiallyat its. original temperature, While the fluid in pool 18 of the ejectorunit 17 will be heated suilciently to be vaporized, and the vapor willemerge, in the form of streams through the nozzles 2da, Zilb. The vaporstreams trap the molecules of gas or air originally in the inner shell16a, and those which diffuse intoV the shell from the system to beexhausted. The downward moving vapor streams carry the air or' gas downto the region where the fore-vacuum pump is effective to remove the gasandpass it to the atmosphere. Relatively high vacua can be obtained withthis singlestage'vapor-entrainment pump system.

The cooling 'jacket 13, aided by the optional jackets a, 25b,7condensesthe vapor streams which thus return in liquidl state along the innerwalls of the shell 19a into the`V reservoir 11. The entraining iluid isconsequently used over and over.

Byheating only the'small volume Vof liquid in poolv 18r to generate thevapor streams, the, large reservoir of liquid and the housing structure,generally, will be norapparatus may then be quickly restored to ambientternperature at-the conclusion'of an operation.' This representsanimportant feature of the invention.

In FIG. 2, another embodiment of a single-stage vaporentrainment pumpisshown, where a conductive liquid metaLcg. mercury, is used `forentrainment. Here the housing or shell 50 has a narrow bottom portion 51serving as'a reservoir for the mercuryA 52. v,The coolingV v jacket 533khas an inlet 53a and an outlet 53h arranged in a fashionsimilar to thatshown in FIG.` 1, with the difference, however, that the jacket of thisembodiment surrounds only the upper portion of the pump structure 59.The fore-vacuum and high-vacuum apertures are designated 54 and55,.respectively.

In this system, an electromagnetic pump56 is applied to raise themercury 52 from the reservoir 51 into a tube 56h.k The pump 56 comprisesan armature 56C which carries a coil 56d which is ed from an A.C.electric source 63. vThe alternating magnetic held-between poles 56e ofthe armature 55C imparts a pulsatingrmo'tion to the mercury within athroat Sf ofY the tube 56b, whereby the mercury is forced up through thetube 56b into apool 58 in a recessed portion 57C of the ejector unit 57.ln this embodiment, the ,mercury inthe poolV 58 is heated by means ofVYan arc discharge produced between an electrode 59a reaching into thepool 58 and themercury itself; the current is led from a source ofcurrent 61 through a regulator means l62 to the electrode 59a on the onehand and to the ejector-unit body on the other,

' the latter being provided with a terminal 59h. VElectrode j 59a isinsulated from'theV unit 57; terminal 59h with the corresponding pole ofsource 61 is kept at ground potential, Vso that there will be nointerference with other electrically conducting parts.

The ejector unit 57 Vhas nozzles tla, 691: and an over ow tube 64carrying the excess mercury back tothe reservoir'Sl. In this embodiment,no additional cooling jackets are shown for the tubes 56h ando-4,although, it is to be understood, the cooling eiect can be achieved inythe same manner as in the Vprevious illustration.

'I'hevapor-entrainment pump, according to the presentrinvention, mayalso be arranged in a single stage or Y in several stages ofamulti-stage'pump, as schematically illustratedrin'FIG. 3.Thisembodiment is provided with a preliminary liquid-jet stage 77, anoptional vaporor liquid-jet stage 37 and two ditusion stages 97 and 97',both of the latterk being similar to the ejector yunit 17 shownin HG. 1.The stagev77 has Ya construction Si) The entire for the passage of theentraining uid; stages 77 and are connected in series with the followingparallel-acting stages 97 and 97. all the remaining stages are suppliedby a delivery pump, or pumps 76 which have an inlet tube 7621 reachinginto the tiuid 72 contained in a reservoir 71,V these elements beingsimilar to the respective elements 16, 15a, 12 and 11 of themst-described embodiment. In Ya similar way, the pump` housing or shell79, the cooling jacket 73, its

connections 73a, 7311, the fore-vacuum connection 7.4 and thehigh-Vacuum aperture 75 all correspond to their counterparts 1t?, 13,13a, 13b, 14 and 15, respectively,

of the i'lrst embodiment.

Owing to constricted nozzles 96a md 9i b of the vaporjet stage S7, thisstage may be operated at a high pressure. An ample amount of Ventraininguid is supplied by the delivery pump, or pumps 76 through a riser tubedb. Similar and parallel riser tubes 96b and 95h' are provided from thesame delivery pump, or pumps to the ditusion stages 97 and 97",respectively. All riser tubes `have respective valve means 31, 91 and 91individually i Y the sake of clarity, the supporting'flanges 17a, 17b,the

electric connections 21-23 to the heaters, and otherV structural detailsof FIG. l have been omitted fromthe Y' somewhat'schematic showing ofFIG. 3. y

When the heating element 89 of stagey 87 is disconnected, this stagewill perform as a liquid-jet stage; with the heater on, the iluid 72will be .vaporized as in the diffusionrstages, so thatV the nozzles 90a,90b will perform as vapor jets.

In ajmulti-stage entrainment-pump according to this invention, a veryhigh'pumping stability is attained Vowing to the provision of theadjustable valve means 81, 91, 91'V which will allow the requiredindividual pressure valuesk to be maintained forall stages withoutoverloading them.

The stability can be increased by incorporating suitably selectedowresistances into the ,fluid riser tubes or by other control means, eg.by providing the riser tubes With predetermined cross` sections. j

It will be obvious to those skilled in the art that various changes andmodilications may be, made in theV vaporentrainment pumps according tothis invention withoutA departing from the invention in its broaderaspects. It w11l be appreciated, for example, thatV the conveying,

heating and ejector means may be substituted by other' equivalent means,e.g. a high-frequency heater or a steam coil maybe used, fed byrespective external sources.

Also, the Vlast-described embodiment may be yprovided prising anenclosing shell, a reservoir in thelower portion j of sa1d shell, avaporizable iluid in said reservoir, ejector means for the vapor thusobtained in said upper portionY of said shell, said shell having, belowsaid-ejector means, a fore-vacuum port connectable to an externalpressurereducing means of a known type, and having, above said` ejectormeans, a low-pressure port connectable to theV system to be evacuated,Vintermediate storage means between said lower and upper portions ofsaid shell, iluid conveying means between said reservoir and saidintermediate storage means for raising said uid from said Except for theliquid-jet stage 77,-

reservoir to said intermediate storage means, said intermediate storagemeans being in fluid communication with said ejector means, heatingmeans provided for said huid in said intermediate storage means tovaporize said raised luid, whereby the vapor leaving the ejector meanswill entrain molecules of the gas v ithin the pump and guide them downto the region of the fore-vacuum port through which they are passed tothe atmosphere, and a cooling jacket surrounding at least said upperportion of said shell and adapted to condense said vapor into fluid forreturn into said reservoir, and only a small proportion of the totalamount of said vaporizable iluid is heated at one time.

2. A vapor-entrainment pump, according to claim 1 wherein said conveyingmeans for the duid comprises a centrifugal pump, an inlet tube of saidpump reaching into said reservoir and an outlet tube of said pump beingconnected to said intermediate storage means.

3. A vapor-entrainment pump, according to claim 1, wherein saidconveying means comprises a duid displacement pump, an inlet tube ofsaid pump reaching into said reservoir and an outlet tube of said pumpbeing connected to said intermediate storage means.

4. A vapor-entrainment pump, according to claim 1, further comprisingcooling means disposed adjacent to at least part of said conveyinfrmeans, for accelerating die condensation of said vapor after it emergesfrom said ejector means.

5. A vapor-entrainment pump, according to claim 1, further comprising anoverflow tube leading from said intermediate storage means to said lowerportion of said shell, whereby the excess quantity of the lluid raisedby said conveying means is returned to said reservoir.

6. A vapor-entrainment pump, according to claim 5, further comprising asecond cooling jacket around said overflow tube for equalizing thetemperature difference of said duid within said reservoir and saidejector means.

7. A vapor-entrainment pump, according to claim 1, wherein said iiuid isa conductive liquid metal, and said conveying means comprises anelectromagnetic pump raising said liquid metal from said reservoir tosaid ejector means, an inlet tube of said pump reaching into saidreservoir and an outlet tube of said pump being connected to saidintermediate storage means.

8. A vapor-entrainment pump, according to claim 7, wherein said heatingmeans comprises at least one electrode connected to a source of electriccurrent and contacting a pool of said liquid metal within saidintermediate storage means so as to vaporize said liquid metal.

9. A vapor-entrainment pump for rarefying gases, comprising a pumpshell, a reservoir in the lower portion of said shell, a vaporizablelsluid in said reservoir, a plurality of ejector stages within said pumpshell, each having iluid storage and heating means for storage andheating of part of said vaporizable huid, separately controllable conve*ing means for said iluid storage means of each of said plurality ofejector stages, delivery pump means adapted to deliver said vaporizablefluid to the fluid storage means of said ejector stages via saidconveying means, a highpressure port in said shell below said ejectorstages, said high-pressure port being adapted to be connected to an eX-ternal pressure reducing means of a known type, and a low-pressure portabove said ejector stages, whereby said part of said tluid in saidstorage means of at least one of said ejector stages is vaporized bysaid heating means associated with said storage means and the uidbecomes vaporized and said vaporized uid is emitted through the ejectorstage to entrain gas molecules sucked through said low-pressure port andpass them through said high-pressure port.

10. A Vapor-entrainment pump, according to claim 9, wherein saidcontrollable conveying means comprises inlet tube means of said deliverypump means reaching into said reservoir rmd a plurality of outlet tubesof said delivery pump means, each outlet tube being connected to one ofsaid ejector stages, and control means for regulating the amount or"huid delivered by said delivery pump means to each of said eje torstages.

11. A vapor entrainment pump according to claim 10, wherien saiddelivery pump means comprises a plurality of delivery pumps, and saidinlet tube means comprises an inlet tube for each of said deliverypumps.

12. A vapor-entrainment pump, according to claim 9, further comprisingcooling means connected to at least part oi said shell and of saidconveying means adapted for temperature compensation between thevaporized and liquid portions of said huid.

13. A vapor-entrainment pump, according to claim 9, further comprisingan overilow tube leading from at least one of said ejector stages tosaid reservoir, whereby the excess quantity of the fluid raised by saiddelivery pump means and said conveying means is returned to saidreservoir.

References Cited in the ille of this patent UNITED STATES PATENTS

1. A VAPOR-ENTRAINMENT PUMP FOR RAREFYING GASES, COMPRISING AN ENCLOSINGSHELL, A RESERVOIR IN THE LOWER PORTION OF SAID SHELL, A VAPORIZABLEFLUID IN SAID RESERVOIR, EJECTOR MEANS FOR THE VAPOR THUS OBTAINED INSAID UPPER PORTION OF SAID SHELL, SAID SHELL HAVING, BELOW SAID EJECTORMEANS, A FORE-VACUUM PORT CONNECTABLE TO AN EXTERNAL PRESSUREREDUCINGMEANS OF A KNOWN TYPE, AND HAVING, ABOVE SAID EJECTOR MEANS, ALOW-PRESSURE PORT CONNECTABLE TO THE SYSTEM TO BE EVACUATED,INTERMEDIATE STORAGE MEANS BETWEEN SAID LOWER AND UPPER PORTIONS OF SAIDSHELL, FLUID CONVEYING MEANS BETWEEN SAID RESERVOIR AND SAIDINTERMEDIATE STORAGE MEANS FOR RAISING SAID FLUID FROM SAID RESERVOIR TOSAID INTERMEDIATE STORAGE MEANS, SAID INTERMEDIATE STORAGE MEANS BEINGFLUID COMMUNICATION WITH SAID EJECTOR MEANS, HEATING MEANS PROVIDED FORSAID FLUID IN SAID INTERMEDIATE STORAGE MEANS TO VAPORIZE SAID RAISEDFLUID, WHEREBY THE VAPOR LEAVING THE EJECTOR MEANS WILL ENTRAINMOLECULES OF THE GAS WITHIN THE PUMP AND GUIDE THEM DOWN TO THE REGIONOF THE FORE-VACUUM PORT THROUGH WHICH THEY ARE PASSED TO THE ATMOSPHERE,AND A COOLING